In the German patent DE 102 60 720 A1, a method for operating a lambda sensor is described, which is intermittently operated with a reduced setback operating temperature, whereat a thermodynamic equilibrium can be set in the region of the electrodes. The at least intermittent operation of the lambda sensor with the setback operating temperature changes the cross sensitivity of the lambda sensor with respect to the cross sensitivity at the nominal operating temperature. This effect can be utilized to develop or suppress cross sensitivities of the lambda sensor in certain operating situations of the internal combustion engine, in whose exhaust gas channel the lambda sensor can be disposed. The CH4-cross sensitivity of the lambda sensor can, for example, be reduced with the setback operating temperature if the internal combustion engine is temporarily operated with a rich air/fuel mixture within the scope of the regeneration of a NOx storage catalytic converter. The setback operating temperature is specified by means of an intervention into the control circuit of the sensor heating device.
In the German patent DE 103 31 158 A1, a method for operating a lambda sensor is described, whose electrodes are intermittently impinged with an externally impressed regeneration current. It has been proven on the basis of experiments that a cleaning effect on the electrodes of the lambda sensor can thereby be achieved, which contributes to an extension of the time in service of the lambda sensor.
In the German patent DE 199 41 051 A1, a wideband lambda sensor is described, which has a sensor chamber, which is connected to a gas chamber via a diffusion barrier. An inner pump electrode is disposed in the sensor chamber. Said electrode together with an outer pump electrode and an electrolyte, which lies between the pump electrodes and conducts oxygen ions, comprises a pump cell. Oxygen ions can be pumped via the electrolyte out of the sensor chamber or into the sensor chamber with the pump cell. Beside the pump cell, a measuring cell is present, which lies between the inner pump electrode and the reference gas electrode, an electrolyte, which conducts oxygen ions, being likewise disposed between the inner pump electrode and the reference gas electrode. The measuring cell corresponds to a Nernst cell, whereat the potential difference developing in the thermodynamic equilibrium between the inner pump electrode and the reference electrode is proportional to the logarithm of the ratio of the partial pressure of the gas being tested in the sensor chamber and the partial pressure of the gas being tested in the air reference. The aim of a measurement of the exhaust gas lambda is to influence the oxygen partial pressure in the sensor chamber in such a way that the Nernst potential constantly remains at a specified value, which preferably corresponds to Lambda=1. A circuit arrangement makes sure that a pump current can flow. The polarity and the absolute value of the pump current depend on which value the specified Nernst potential has exceeded or undershot. The pump current which arises is a measurement for the exhaust gas lambda.
The German patent DE 199 60 731 A1 describes a NOx sensor which contains at least some components, whose operating modes are identical to the corresponding components of a lambda sensor.
The task underlying the invention is to state a method for operating an exhaust gas sensor, which is preferably provided for arrangement in the exhaust gas of an internal combustion engine, and a device for carrying out the method. Said method and device are thus provided to increase the reliability of the sensor signal of the exhaust gas sensor.